Although it's a popular online "wholesale" marketplace (this rather long DHGate review describes the features in detail), DHGate is not the most popular source of products for most of the e-commerce stores that are set up with Shopify.
While many thousands re-sell products from Ali Express, the main rival to DHGate, nowhere near as many buy goods from DHGate – which makes it a somewhat untapped source of low cost products.
The main reason for this is not a lack of products on DHGate, neither is it related to lower quality products, unreliable sellers or a website that's difficult to use. DHGate has all the same features that Ali Express has, and a similar number and range of products.
The reason so many Shopify store owners use Ali Express instead of DHGate an app called Oberlo. Oberlo is a Shopify app that's designed to import products from Ali Express into a Shopify store – but not only that, you can use Oberlo to manage your inventory, automatically update prices and even fulfil orders directly with your suppliers.
Oberlo is so easy to use and efficient that it's the key component in many Shopify drop shipping stores – and it's only available to use with Ali Express, not DHGate.